JPH05127711A - Programmable controller - Google Patents

Abstract

(57) [Abstract] (Modified) [Configuration] A plurality of signal input terminals 4 for receiving signals from a plurality of external input devices, and power supply terminals 8 exposed to the outside for supplying power from the outside. Ground terminal 5
In a programmable controller including an input circuit having a constant current element 13 disposed between the power supply terminal 8 or the ground terminal 5 and the plurality of signal input terminals 4. [Effect] The power supply voltage range supplied to the input circuit can be widened, and various external input devices can be connected without changing the internal circuit. By incorporating a plurality of fixed power supplies that are used for general purposes, the user does not need to specially prepare the power supply, and the labor such as wiring can be saved. It can be easily matched to the specification form of the external input device, and is easy to handle. The photocoupler may be an economical one-way type, and the programmable controller can be configured at low cost. Further, the transmission ratio can be made constant and stable performance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a programmable controller, and more particularly to an input circuit of a programmable controller for selecting a power source voltage of an external signal so that various external input devices can be used.

[0002]

2. Description of the Related Art Generally, a programmable controller, as shown in FIG. 6, has an input section 1 for taking in signals from external input devices 2 and 3 (the output sections thereof are shown by electronic switches and contacts). A control unit 100 that performs arithmetic processing on a signal captured by the input unit 1, and the control unit 1
00 sequence processing storage unit 102 that stores a sequence program that defines the procedure of arithmetic processing, and an output unit 103 that transmits the arithmetic processing result of the control unit 100 to the external load 104 based on the contents of the storage unit 102. There is. The sequence program stored in the sequence program storage unit 102 has been programmed and transferred in advance by the programming device 101.

The input circuit in the input section 1 of such a programmable controller is conventionally a circuit as shown in FIG. 7, which includes a power source 9, a limiting resistor 106, and a photo-transmitting optical signal for the purpose of insulation. It is composed of a coupler 18, a capacitor 22 for removing noise, a resistor 21, and a limiting resistor 20 of the photo coupler.

In such a configuration, the external input device 2
Alternatively, if the voltage specification of 3 is different, the transfer characteristic of the photocoupler 18 is changed, so the value of the resistor 106 must be changed, and if the value of the resistor 106 is made constant, the resistor 106 is proportional to the square of the power supply voltage 9. There is a problem of heat generation. As a method for solving this problem, there is a technique described in Japanese Utility Model Laid-Open No. 64-46805. In this technique, two common terminals are provided for the input terminal, and one of the two types of DC input voltage is selected according to the proper use of the common terminal.

Further, in Japanese Laid-Open Patent Publication No. 59-146305, a constant current circuit is connected in series to an LED on the input side of a photocoupler, so that various kinds of input signal voltages having different voltage values can be input. A technique is disclosed in which the current supplied to the side LED is made substantially constant.

Further, in Japanese Laid-Open Patent Publication No. 1-237702, the level of the input signal voltage fluctuates by changing the magnitude of the detection reference threshold voltage of the input signal voltage in the voltage control circuit according to the fluctuation of the input voltage level. However, a technique for surely detecting the input signal voltage is disclosed.

[0007]

In the known example described in the above-mentioned Japanese Utility Model Publication, the input voltage specification is fixed to two kinds of voltages, for example, 24V and 12V, and the external signal of the TTL circuit (5V system) is taken in. In this case, there is a drawback that the resistor 106 shown in FIG. 7 must be changed in order to flow the specified current. In addition, a 24V power supply which has been generally used conventionally must be prepared externally so that the power supply is not fixed to one type, which is extremely inconvenient for a user who uses a programmable controller.

Further, according to the prior art of Japanese Patent Laid-Open No. 59-146305, it is not necessary to change the resistor 106, but when the constant current circuit as disclosed is used for each photocoupler, an external input is used. As the number of points increases, the mounting area increases and there is a problem in terms of cost.

Further, in any of the known examples described above,
The direction in which the current of the photo coupler flows is fixed, and the specifications of the external input device, such as current sink type (sink type) and voltage output type (source type), have different parts or the cost is high. There was a problem that it had to be a photo coupler.

An object of the present invention is to provide a programmable controller equipped with an input circuit which can handle a plurality of input voltages without changing any parts and can make the mounting area relatively small.

Another object of the present invention is to provide a programmable controller having an input circuit which can be used without changing parts regardless of whether the external input device is a sink type or a source type. Especially.

[0012]

In order to achieve the above object, a programmable controller according to the present invention is provided with a plurality of signal input terminals for receiving signals from a plurality of external input devices and a power supply for supplying power from the outside. In a programmable controller including an input circuit having a terminal and a ground terminal, a constant current element is arranged between the power supply terminal or the ground terminal and each of the plurality of signal input terminals.

The programmable controller preferably further includes a reference voltage generation circuit for generating a reference voltage based on the voltage supplied to the power supply terminal, and the reference voltage and the voltages of the plurality of signal input terminals, respectively. A plurality of comparators for comparison and a plurality of photocouplers driven by the outputs of the plurality of comparators are provided.

Further, at least one other power supply terminal exposed to the outside is provided, and at least one built-in power supply connected between the power supply terminal and the ground terminal is provided, and the other power supply terminal is the above-mentioned. By connecting to the power supply terminal, the built-in power source can be used instead of the external power source.

Each of the constant current elements may be a bidirectional constant current element, and a changeover switch for switching whether the bidirectional constant current element is connected to the power supply terminal or the ground terminal may be provided.

Alternatively, each of the constant current elements is constituted by a pair of constant current elements for flowing current in the opposite direction, one end of each of the pair of constant current elements is commonly connected to the signal input terminal, and the other end thereof is connected. May be connected to the power supply terminal and the ground terminal, respectively.

A resistor may be connected in parallel with the constant current element.

[0018]

The constant current element has a property that when a voltage is applied, the internal impedance changes according to the voltage and a constant current flows. Therefore, it is possible to apply an arbitrary voltage to the circuit while maintaining the current flowing through the signal input terminal constant without replacing the resistance or the like. Therefore, it is not affected by the length of the signal line, and the resistance to noise is not impaired.
Further, the constant current element is a small single element, and its mounting area is smaller than that of the conventional constant current circuit in which several elements are combined, which contributes to downsizing of the programmable controller.

Further, by preparing a power supply voltage having a relatively high frequency of use as an internal power supply so that it can be used as a power supply in place of an external power supply, user convenience can be achieved.

Since the comparator is used, the LE of the photocoupler is used.
The power supply voltage of D can be set separately from the power supply voltage of the input circuit, and the ON current of the LED can be kept constant. Similarly, by using the comparator, the switching of the current direction depending on whether the external input device is the source type or the sink type can be performed regardless of the current direction of the LED of the photocoupler. Switching according to the type of the external input device can be performed by switching the polarity of the power source for the external input device and switching the direction of the constant current element (or adopting a bidirectional constant current element). Although the polarity of the signal output from the photocoupler is inverted depending on the type of external input device, this can be dealt with by inverting the output signal of the photocoupler for one type. This inversion process can be easily performed by software or hardware.

By arranging the resistor in parallel with the constant current element, the current value can be increased even when the rated current of the constant current element is small.

[0022]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 7 shows the configuration of an embodiment of the programmable controller according to the present invention. In the figure, the same elements as those in FIG. 6 are designated by the same reference numerals. The characteristic of this programmable controller is the portion of its input circuit 1, and its configuration will be described with reference to FIG. 1 which is shown separately.

In FIG. 1, as in the case of FIG. 6, 1 is an input unit and 2 and 3 are external input devices. 4 is an input terminal for connecting a signal line from the external input device group,
A plurality of input terminals 1, 2, ..., N are provided.

Reference numeral 5 is a 0 V terminal (ground terminal) to which one side of the external input device groups 2 and 3 is commonly connected.

Reference numerals 9 and 10 are 12V, which are often used in a general 24V power source and a 12V encoder.
It is a power supply and is built in the programmable controller in this embodiment. The negative terminals of the power supplies 9 and 10 are commonly connected to the 0V terminal. Reference numerals 6 and 7 are terminals connected to the positive terminal of the power supply 9 and the positive terminal of the power supply 10, respectively, and are arranged on the outer surface of the programmable controller. Reference numeral 11 is a power supply of another voltage supplied from the outside as needed.

Reference numeral 8 is a power supply terminal for supplying power to an internal circuit, which will be described later.

Reference numeral 12 denotes a protection diode in the case of the external power supply 11 which is erroneously connected in reverse polarity.

Reference numeral 13 is a constant current element provided for the purpose of the present invention, and a constant current diode is an example thereof.
This characteristic has a property that when the applied voltage changes, the internal impedance changes, and a constant current is always supplied.
In the case of FIG. 1, for the sink type input device, the direction of the constant current diode is connected so that the cathode is on the input terminal 4 side.

The necessity of the "constant current" will be described. For example, when the external input devices 2 and 3 are TTL outputs (use voltage is 5 V), the longer the wiring length, the higher the impedance and the poor noise resistance performance. Therefore, it is necessary to flow a predetermined current (8 mA). Also, external input devices 2, 3
If is a contact point, considering the reliability of the contact point, the current value is a very important factor such as 8 mA is required at a voltage of 24V. Therefore, in such a case, an 8 mA type element may be used as the constant current element.

Reference numeral 14 is a protective resistor, and 15 and 16 are resistors for generating a reference voltage of a comparator which will be described later. For example, 15
If the values of (R1) and 16 (R2) are set to R1 = R2, half of the working voltage (power supply voltage connected to the power supply terminal 8) becomes the threshold voltage, and the noise resistance performance against impedance change due to wiring becomes good. ..

Reference numeral 17 is a comparator group, and the number of comparators corresponding to the number of input terminals 4 is provided. Each comparator compares the signals from the external input devices 2 and 3 with the reference voltage, and outputs the result as a binary value (“0” or “1”). In this embodiment, when the external input devices 2 and 3 are "ON", the output of the comparator is "0" = LOW level voltage, "OF".
In the case of F "," 1 "= HI level voltage.

Reference numeral 18 is an element for optically transmitting a signal, in which a light emitting element and a light receiving element are integrated, which is commonly called a photocoupler. Each photocoupler 18 is driven by the output of the corresponding comparator.

Reference numeral 19 is a limiting resistor for limiting the current flowing through the LED of each photocoupler 18, which is connected to the positive terminal of one of the plurality of power supplies (here, 24V power supply 9) built in the programmable controller. Then, when the comparator 17 is turned on, a current limited to a constant current flows into the LED of the photocoupler 18, and the signal is transmitted to the subsequent stage. Two
Reference numeral 0 is a limiting resistor on the light receiving side of the photocoupler 18. Two
Reference numerals 1 and 22 are resistors and capacitors for removing chattering and the like of the external input signals 2 and 3, and constitute a chattering removing circuit.

Reference numeral 23 denotes an interface unit to the above-mentioned control unit 100, which shapes the waveform of the signal from the chattering removal circuit and switches to the counter circuit 24. The counter circuit 24 is configured to count up and down the high speed pulse when the external input device is one that generates a high speed pulse like an encoder. 3 input signals of marker signal. Interface unit 23
Has a function of switching its operation according to an instruction from the control unit 100 so that the input signal can be treated as a normal input signal when the counter function is not used.

Reference numeral 25 is a switching portion provided on the pattern of the printed circuit board that houses the circuit of this embodiment. As shown in FIG. 1, when the external input devices 2 and 3 are of the sink type described above, they are connected to the "A" side by a jumper wire, a zero ohm resistor or the like. On the contrary, in the case of the source type, as will be described later with reference to FIG.

Now, in the circuit of FIG. 1, the power supply will be described.
4 V), the connection shown in FIG. 1 (between 24 V and S) is made using a short bar or the like. If the external input devices 2 and 3 operate at 12V like an encoder, the connection (between 12V and S) is performed and the connection is not performed.

If the external input device is TTL (5V) or the like, a 5V external power supply 11 is prepared and connected (S to 0).
(Between V). At this time, and are not connected.

The terminals 5 to 8 for making these connections are exposed and arranged on the external surface of the programmable controller, and can be freely connected by the user according to the purpose.

Regarding the three terminals 6, 7, and 8,
The power supply terminal 8 is arranged at the center so that the terminals 6-8 or the terminals 7-8 can be selectively connected by the short bar or the like.

According to the present embodiment, the constant current element 13 allows a constant current to flow through the input terminal 4 regardless of the power supply voltage used, without changing the components. However, in the present embodiment, the current flowing in the input terminal 4 is not directly applied to the LED of the photocoupler 18, but the comparator 1 is provided between the input terminal 4 and the photocoupler 18.
7 is used. Therefore, as described above, the LED of the corresponding photocoupler 18 is driven according to the comparison result of the reference voltage obtained by the resistors 15 and 16 and the voltage of each input terminal 4. By using a specific power source (24V power source 6 in this embodiment) as the driving power source of the LED, the current value when the LED is turned on can be made constant.

FIG. 2 shows a case where the external input devices 2 and 3 are the source type described above. The switching unit 25 is connected to the "B" side, and the connection direction of the constant current element 13 is reversed.

In this case, it is sufficient to change the connection of the jumper wire or the like of the switching unit 25 in terms of mounting, but the output of the comparator 17 is inverted and the output to the control unit 100 is also reversed in terms of signals. This can be dealt with by an inversion circuit in hardware or software inversion processing in the interface unit 23. For example, although not shown, the hardware inverting circuit takes in a signal from the switching unit 25 into the single interface unit 23 and takes a plurality of exclusive ORs that take the exclusive OR of this signal and each output of the chattering removal circuit.
It can be easily realized by providing a circuit.

FIG. 3 shows a second embodiment of the present invention. In the figure, 26 is a bidirectional constant current element, and 27 is a changeover switch.

The bidirectional constant current element 26 has two built-in constant current elements 13 described above, and forms one package. The characteristics are the same, but a constant current can flow in both directions.

The change-over switch 27 can be changed over from the external surface of the programmable controller, and can be selectively used depending on whether the external input device 2 or 3 is the sink type or the source type.

Here, the "A" side of the changeover switch 27 is the sink type and the "B" side is the source type.

The other points are the same as those in the first embodiment, and the description thereof will be omitted.

Although the bidirectional constant current element 26 is a one-package product, it may be one in which two constant current elements 13 are used and are reversely connected in parallel.

Further, the inversion of the signal in the interface section 23 may be performed by the above method.

Next, a third embodiment of the present invention will be described with reference to FIG.

In the present invention, instead of the switching unit 25 according to the first embodiment, constant current elements 13 'having different directions from the constant current element 13 are provided and connected to the points "A" and "B", respectively. It is a thing. This eliminates the need for switching switches or the like depending on the type of external input device. The inversion of the above signal is the same as described above.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

The present invention is provided with a shunt resistor 28 in parallel with the constant current element 13 according to the first embodiment, and is otherwise the same as the first embodiment. Shunt resistance 28
The role of is to increase the circuit current when the current value of the constant current element 13 is insufficient, for example, with the current value of 8 mA as described in the first embodiment. For example, when a minimum of 10 mA is required, it is a shunt resistance for increasing 2 mA. The resistance value may be determined by the minimum voltage of the power supply voltage used.

Obviously, the third embodiment can be applied to the second embodiment.

Next, in the first, second and third embodiments described above, the limiting resistor 19 will be described in detail. The photocoupler 18 has a characteristic that the transmission ratio changes depending on the magnitude of the current passed through the light emitting side LED. Therefore, in the signal transmission of the programmable controller, the transmission speed and ON of the light receiving side
Since it is related to the / OFF voltage value, it is desirable that it is constant. As described above, in the embodiment of the present invention, the limiting resistor 19 is included in the power source 9 built in the programmable controller.
Is connected, and when the comparator 17 is turned on, a constant current flows, which is preferable.

[0057]

As described above, according to the embodiment of the present invention, (1)
The power supply voltage range supplied to the input circuit can be widened, and various external input devices can be connected without changing the internal circuit. (2) By incorporating a plurality of fixed power supplies that are used for general purposes, the user does not need to specially prepare the power supply, and the labor such as wiring can be saved. (3) The specification form of the external input device can be easily matched, and it is easy to handle. (4) The photo coupler may be an economical one-way type, and the programmable controller can be configured at low cost. Further, the transmission ratio can be made constant and stable performance can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first input circuit of a programmable controller of the present invention.

FIG. 2 is an explanatory diagram of an application example of the input circuit of FIG.

FIG. 3 is a circuit diagram of a second input circuit of the programmable controller of the present invention.

FIG. 4 is a circuit diagram of a third input circuit of the programmable controller of the present invention.

FIG. 5 is a circuit diagram of a fourth input circuit of the programmable controller of the present invention.

FIG. 6 is a block configuration diagram of a general programmable controller.

FIG. 7 is an input circuit diagram for explaining a conventional example.

FIG. 8 is a block diagram showing a configuration of an embodiment of a programmable controller according to the present invention.

[Explanation of symbols]

5 ... 0V terminal, 6, 7 ... power supply terminal, 8 ... power supply terminal,
13, 13 '... Constant current element, 19 ... Limiting resistance, 25 ... Switching unit, 26 ... Bidirectional constant current element, 27 ... Changeover switch,
28 ... Shunt resistance

Claims (9)

[Claims] 1. A programmable controller including an input circuit having a plurality of signal input terminals for receiving signals from a plurality of external input devices, and a power supply terminal and a ground terminal to which power is externally supplied. A programmable controller in which a constant current element is arranged between a terminal or a ground terminal and each of the plurality of signal input terminals. 2. A reference voltage generation circuit that generates a reference voltage based on a voltage supplied to the power supply terminal, and a plurality of comparators that compare the reference voltage and the voltages of the plurality of signal input terminals, respectively. 2. The programmable controller according to claim 1, further comprising a plurality of photocouplers each driven by an output of the plurality of comparators. 3. The programmable controller according to claim 2, wherein a predetermined constant voltage is used as the power supply voltage of the input side LED of the photocoupler. 4. The programmable controller according to claim 1, wherein which of the power supply terminal and the ground terminal the constant current element is connected to is switched by a jumper wire. 5. At least one other power source terminal exposed to the outside is provided, and at least one built-in power source connected between the power source terminal and the ground terminal is provided, and the other power source terminal is provided. The programmable controller according to claim 1, wherein the built-in power source can be used instead of the external power source by connecting to a power source terminal. 6. The programmable controller according to claim 5, wherein the voltage of the built-in power supply is used as the power supply voltage of the input side LED of the photocoupler. 7. The bidirectional constant current element is used as each of the constant current elements, and a changeover switch is provided for switching which of the power supply terminal and the ground terminal the bidirectional constant current element is connected to. The programmable controller according to claim 1. 8. A pair of constant current elements that flow current in the opposite direction constitute each of the constant current elements, one end of each of the pair of constant current elements is commonly connected to the signal input terminal, and the other end of each is connected. 2. The programmable controller according to claim 1, wherein the programmable controller is connected to the power supply terminal and the ground terminal, respectively. 9. The programmable controller according to claim 1, further comprising a resistor connected in parallel with the constant current element.